In the early 1960s, long-term hemodialysis was introduced for the treatment of irreversible kidney failure. Early in the evolution of this procedure, it was recognized that self-treatment in the home offered important advantages over treatment provided in a dialysis facility. These advantages include recognition that treatment at home could be more cost-effective than care in a dialysis clinic or facility, and the belief that self-care at home would provide a better, more independent lifestyle since the patient could control scheduling of treatment and other important aspects of the therapeutic process.
Hemodialysis treatment is employed as a therapeutic measure when a patient's kidneys no longer perform their blood purifying function because of disease or traumatic removal. Kidney failure results in the accumulation of toxic waste in the patient's blood and eventual death from uremic poisoning, unless the waste material is removed by some artificial means. In hemodialysis, the patient's blood is circulated on one side of a membrane contained within a hemodialyzer (i.e., artificial kidney). The membrane has pores of microscopic size through which waste products from the blood pass. The pores are, however, too small to permit blood cells and proteins to leave the body. A dialysis fluid (dialysate) is circulated on the other side of the hemodialyzer membrane to remove the waste products.
Most kidney failure patients require dialysis treatments three times weekly. Thus hemodialysis treatment requires a significant time commitment by each patient. One attempt to shorten each treatment has been made with high efficiency hemodialysis such as high-flux hemodialysis. High-flux hemodialysis increases the efficiency of hemodialysis by increasing blood flow to the maximum rate possible and by using high-efficiency hemodialyzers. High-flux hemodialysis requires accurate control of filtrate removal rates from the patient, and thus is only able to be conducted with special machines under the careful guidance of skilled medical personnel and is rarely performed in the home. Another example of high efficiency hemodialysis is hemodiafiltration. Hemodiafiltration is a combination of hemodialysis and hemofiltration.
The use of a dialysis machine at home requires the presence of a trained helper to assist with the preparation of the hemodialyzer and associated apparatus both before and after each hemodialysis treatment. The helper usually must remain vigilant throughout the therapeutic process to monitor all of the systems of the hemodialysis machine. It is difficult for the patient to adequately and effectively monitor all of the systems, because a drop in blood pressure, for example, may leave the patient physically unable to respond.
The advantages of home dialysis treatment include important scheduling and lifestyle benefits. These real benefits should have made this form of treatment extremely popular. However, home hemodialysis has failed to achieve the popularity originally envisioned. This is due to several interrelated factors.
(1) The safety of the home dialysis procedure is perceived by patients to be inadequate. For example, small air bubbles may collect in the blood circuit of the system. These must be manually removed by the patient or the helper to prevent their passage into the body via the venous line. The passing of air bubbles into the body could be a life-threatening event.
(2) There is confusion by many patients about dialysis machine operation. This is especially true with regard to adjustment of the blood pump to a rate sufficient for effective treatment yet not so fast that the pumping rate exceeds the ability of the body to provide blood to the pump. If the pump rate is too fast, an alarm sounds, necessitating a corrective action sequence which many patients view as complicated and confusing.
(3) Excessive work is required to perform dialysis treatment. Time is required to do step-by-step pre- and post-dialysis machine processing, setup and teardown of the hemodialyzer and blood circuit as well as all the necessary small steps incidental to treatment. The time necessary to prepare each treatment is estimated to be 1 hour to 11/2 hours. This time is in addition to the 3 to 5 hours of actual dialysis treatment that is performed three times each week. For many patients, this additional time is an unacceptable burden. For example, the setup activities include the removal of sterilizing agents and testing for their removal, attachment of sterile saline, and start-up of the apparatus, including an assessment of proper functioning. After dialysis treatment, the apparatus must be flushed and either a replacement blood circuit tubing set installed or steps taken to reuse the blood circuit tubing. Reusing the blood circuit involves cleaning, flushing, testing of circuit integrity, and filling with a sterilizing agent. The dialysis machine must be completely cleaned and sterilized weekly. The weekly maintenance and sterilizing requires 3 to 4 hours.
(4) The responsibility for home treatment is shared between the patient and the helper (e.g., spouse). It is widely recognized that patient independence and sole responsibility for care promote rehabilitation and a sense of well-being. However, for many home dialysis patients, the combination of time requirements to prepare for treatment and the attendant uncertainties about proper use of the dialysis machine often cause significant reliance on the helper and a strong relationship of interdependence. This adds to the stress experienced by the patient and by the patient's family, especially when the spouse serves as the helper.
(5) The dialysis machine is intrusive in the home. The size of contemporary dialysis machines makes it difficult to remove them from visibility to family and friends. Thus, the machine serves as a constant reminder of the patient's affliction and dependency. Coupled to this problem is a requirement that large volumes of dialysate concentrate must be stored for use with the machine. The concentrate is a solution of inorganic and organic chemicals which are proportionally mixed with water by the machine to produce the dialysis rinsing solution, called "dialysate," which flushes the machine during treatment. Concentrate volume increasingly is a limiting factor to home treatment due to the widening trend toward apartment-sized dwellings with limited living space.
The contemporary dialysis machine has a blood circuit comprising a blood pump, a hemodialyzer, and usually one or two drip chambers. During treatment, blood is drawn from the patient usually through a needle inserted into a blood vessel in the arm, pumped through the hemodialyzer and drip chamber, and then returned to the patient via a second needle. In the hemodialyzer, the blood passes through one or more chambers, each enclosed by a permeable membrane. A dialysate fluid is simultaneously pumped through the hemodialyzer on the opposite side of this membrane. The toxic components in the blood which are the result of kidney failure pass across the membrane from the blood to the dialysate and are carried away, thereby purifying the blood. The dialysate solution is generally manufactured by mixing treated water with a concentrated solution of several inorganic salts.
In contemporary dialysis systems, usually the blood tubing set is replaced after each treatment. This is due to protein accumulation on the inner walls, especially within the drip chamber, which makes it difficult to clean, and because of physical wear of the walls by the roller blood pump. This wear is increased with improperly adjusted roller blood pumps and may release small fragments of the tubing into the blood stream as microemboli. This complication is greater with silicone rubber tubing. The use of a pumping system that can accurately and reliably pump blood in the blood circuit without significant damage to the wall of the tubing will reduce physical wear on the tubing and hazard from microemboli, and require less frequent replacement. Therefore, there is a need in the art for such an external pump for the blood circuit of a dialysis system.
The blood pump for contemporary dialysis systems is a rotary pump that is set for a specified pumping rate of blood from the patient. The pump rate is usually set below the normal blood output of the patient. The patient's blood flow may drop during treatment below the rate set on the blood pump, which will trigger an alarm and stoppage of the blood pump. Therefore, there is a need in the art for a dialysis blood pump whose pump rate adjusts to the changing output rate of the patient so as to allow a faster treatment time and avoidance of alarms (machine stoppage) due to a drop in patient blood supply.
Another problem for contemporary dialysis systems is the cost and complexity of apparatus required to accurately measure fluid loss during dialysis treatment. Measurements of fluid loss usually are accomplished by weight loss determinations before and after treatment. Some investigators have tried to make better fluid loss determinations by monitoring weight throughout the treatment process. This procedure requires a special weighing bed or chair. Therefore, there is a need in the art for a simple and accurate means to measure fluid loss during treatment.
Further still, a limitation of contemporary dialysis systems is the inability to automatically respond to a fall in patient blood pressure. Technology is available to continuously monitor a patient's blood pressure. However, there is a need in the art to be able to automatically and therapeutically respond to a change in a patient's blood pressure, without relying upon the eventual arrival of help.
Accordingly, there is a need in the art to revise the contemporary dialysis machine and its accompanying fluids to better automate the treatment process so as to allow less vigilance, to expedite or automate the treatment process so that the setup and teardown times can be reduced, and to reduce the physical size of the dialysis system, including the concentrates.